The present invention is generally directed to die boards for use in cutting and creasing sheet-type work materials, and is more specifically directed to a method for fabricating a die board using a rotary cutting tool, and to the materials used in said fabrication.
Die boards are generally used to cut and/or crease one or more layers of sheet-type work material, such as cardboard, for use in the manufacture of various different articles. One such use, given here by way of example and not to be construed as limiting the present invention, is the fabrication of box and package blanks which after having been cut and creased by the die board, can be folded into finished boxes or product packages.
Usually, the die board consists of a base made from a thick piece of material such as plywood, that has a series of slots cut into it. These slots are arranged in a pattern corresponding, for example, to the outer periphery of a box or package blank, and the lines along which the blank must be folded to create the finished box or package. Rules, which generally consist of pieces of steel cut to lengths and/or bent to correspond to the slot length and configurations in the base, are then inserted into and protrude from the slots. The amount by which a particular rule extends from the slot depends on whether the rule will be employed to cut or crease the sheet material. Generally, during a cutting and creasing operation, the sheet material is positioned under the die board and pressure is applied to the board via a press, causing the rules to engage the sheet material, thereby cutting and creasing the sheet material.
In known methods of fabricating die boards, difficulties are often associated with the formation of the slots that must be cut into the die board base to accommodate the rules. Typically these slots are cut into the base in one of two ways; (1) using lasers, or (2) using a jig or band saw. The capital cost of a laser is generally very high, in addition, the use of lasers tends to be expensive and complex. Large amounts of power is required to operate the laser, and the beam must typically be shielded using an inert gas. Another difficulty associated with using lasers is that the slots produced tend to have scalloped edges. When the rules are inserted into these slots, rather than having line contact between the slot edges and the rules; the rules engage the slot edges at discreet points corresponding to the xe2x80x9cpeaksxe2x80x9d of the scalloped edge. This reduces the stability of the rule in the die-board, increasing the potential for inaccurate cutting and creasing when the die board is used. This problem is further exacerbated due to the fact that the heat associated with the laser tends to dry out the board resulting in dimensional distortion of the slots being cut and warping of the board. A further problem also attributable to the heat of the laser is that smoke is generated from the material being cut. The smoke causes environmental problems which must be addressed, resulting in further increases in operating expense.
When a jig or band saw is employed, a starting hole must be drilled at one end of the slot to facilitate insertion of the blade associated with the saw. This requires an additional operation, thereby adding to the cost associated with fabricating the die board. Furthermore, these slots are often cut by hand with the inaccuracies resulting from human error making it difficult to insert the die board rules into the slots. The potential human error can also result in inaccurate die cutting. In addition, when using a manual process, the cut lines must be transferred by hand onto the die board.
Based on the foregoing, it is the general object of the present invention to provide a die board and a method for manufacturing the die board that overcomes the difficulties and drawbacks associated with prior art die boards and their manufacture.
It is a more specific object of the present invention to provide a die board fabricated using rotary cutting tools that is not subject to the above-described inaccuracies.
The present invention is directed to a die board for cutting and/or creasing sheet-type work material that includes a die board base having a first upper surface and a second lower surface. At least one slot extends along the upper surface and through the thickness of the die board base. The slot has a first slot section extending from the first upper surface at least part-way through the die board and having a first slot width at the first upper surface. The slot also includes a second slot section extending from the second lower surface at least part-way through the die board""s thickness and having a second slot width. Preferably, the second slot width is smaller than the first slot width and is adapted to receive and grippingly retain a die board rule. However, the present invention is not limited in this regard as the widths of the first and second slots can also be equal.
In one embodiment of the present invention the die board base is a laminate that includes a first layer of die board material and at least a second layer of die board material. The first layer of die board material includes a third lower surface bonded via an adhesive to a fourth upper surface defined by the second layer. The above-described slot configuration is employed in this embodiment with the second slot section extending through the second layer of die board material. However, the present invention is not limited in this regard as the first slot section can extend through the first and into the second layer of die board material without departing from the broader aspects of the present invention.
Preferably, the second slot section extends through the second layer of die board material, part-way into the first layer of die board material. It is also preferable that the third lower surface of the first layer of die board material have such release characteristics relative to the fourth upper surface of the second layer of die board material that the second layer can be separated from the first layer. In this manner, the adhesive remains bonded to the second layer of die board material, leaving the first layer virtually free of adhesive. Once the second layer of die board material has been separated from the first layer, it can then be attached to the first upper surface, such that the slots in the first and second layers are aligned. Accordingly, when the die board rules are inserted into the die board, the rules are grippingly retained by the slots in the second layer of die board material, as well as by the second slot sections in the first layer of die board material. Retaining the rules at the upper and lower surfaces of the die board has the advantage of increasing the stability of the rule during operation such that rule deflection is minimized.
While the die board has been described above as including first and second layers of die board material, the present invention is not limited in this regard, as any number of layers of die board material can be stacked one-on-top-of-the-other. Moreover, the configuration of the slots can be the same for each layer of die board material, or it can vary. For example, a three layer die board construction can be employed where each slot in each layer includes the above-described first and second slot sections. Conversely, the first and third layers could include only the second slot sections which are adapted to grippingly retain the die board rules, while the second layer of die board material includes only the first slot section that is wider than the second slot section.
The present invention also resides in a method for fabricating a die board wherein a die board base is provided having a first upper surface and a second lower surface. An apparatus, such as, but not limited to a milling machine or router, is also provided to cut the slots in the die board base and utilizes at least one rotary cutting tool. During the die board fabrication process, the die board base is presented to the apparatus which is operated to cause the cutting tool or tools to engage the base. The slots for receiving the die board rules are cut such that each slot includes an upper slot section having a first width, and a lower slot section having a second width that is less than the first width and sized to grippingly retain at least one die board rule therein.
More than one rotary cutting tool can by used to cut the slots into the die board base, however, the present invention is not limited in this regard. For example, a single stepped cutter having an upper cutting portion defining a diameter corresponding to the upper slot width, and a lower tip portion having a diameter corresponding to the second slot width could be used. The cutter could also employ a tapered transition region between the upper cutting portion and the tip portion. While rotary cutting tools have been described, the present invention is not limited in this regard as other cutting methods such as sawing, employing a laser, or using a high-pressure water jet can also be utilized without departing from the broader aspects of the present invention.
The die board base fabricated using the above-described method can also be a laminate comprised of two or more layers of die board material bonded together. In this case, the method would include the steps of cutting the slots into each layer either simultaneously, or one-at-a-time, and then assembling the respective layers, preferably by bonding the layers of die board material together.